Data collection has been completed for a collaborative study of lung cancer and residential radon exposure. Interviews were completed with 1493 lung cancer cases and 1838 controls from Connecticut, Utah, and southern Idaho. Radon measurements were made in past and current homes of participants using year-long alpha-track etch detectors, to estimate cumulative exposure since age 25. Efforts this year focused on retrieving remaining detectors still in homes of participants, and cleaning and transferring data to NIEHS. Methods for imputing missing data, a necessary component in a study such as this which is based on retrospectively obtained exposure histories, have been evaluated through statistical simulations. It has been found that imputing values based on the average radon in all measured homes will allow for unbiased estimation of risk. By also taking into account available information about housing characteristics and residence location (radon potential), we can further improve this estimate so that there is virtually no power loss. In a related study, we evaluated the feasibility of measuring radon using keepsake glass objects and CR-39 technology. Suitable glass objects were measured for 284 subjects. Preliminary correlations between glass and air measurements suggest some bias, but measurements have not yet been corrected for ~background~. Analysis will determine if the presence of smoke in the house affects the reliability of the glass measures. We have also completed data collection in a study of childhood leukemia risk associated with residential radon. Detectors were placed in the homes of 196 cases and 298 controls, representing 82 and 89% of eligible subjects. Preliminary analysis does not support a risk from radon, but analysis has not yet taken into account the amount of time spent at home or other factors that might affect risk. Based on encouraging results from pilot feasibility studies, a large-scale study of cancer incidence in over 18,000 Czech uranium miners has been initiated. Vital status has been ascertained for 2/3 of the cohort to date. Cancer incidence will be evaluated among those found to be alive in 1976. In related work, adverse reproductive outcomes and childhood cancer incidence do not appear to be more common among the offspring of these uranium miners.